Speed control



April 28, 1953 R. 1.. STALLARD SPEED CONTROL Filed Aug. 23, 1949 INVENTOR. ROBERT L. SPILL/4RD Patented Apr. 28, 1953 SPEED CONTROL Robert L. Stallard, Glen Rock, N. .L, assignor to Bendix Aviation Corporation, Teterhoro, N. 3., a corporation of Delaware Application August 23, 1949, Serial No. 111,891

Claims. (01. 322-32) The present invention relates to frequency responsive and more particularly to that type suitable for regulating the speed of a motor or generator.

The invention particularly utlle application in accessories for aircraft as air driven power herein it is sought to operate a throttle for controlling the speed of a prime mover, means of an electric torque motor reto output of an alternator driven by arrangement istrat filed July ill l9, Soil.

'1 by Walter segue, J1.

' ation.

. of the objects of the present invention, ore, to provide means for regulating the of a prime moves by controlling a throttle y of an electric motor responsive to the output of an alternator driven by said prime mover.

Another object of the invention is to provide means for preventing an alternator or motor or the like from overspeeding and to do so in a. novel and effective manner.

Still another object of the invention is to provide a novel and improved frequency regulator circuit contemplatig the use of a resonant circuit to accomplish regulation.

Still another object of the invention is to provide motor regulating means wherebythe varable phase of a torque motor is connected to an alternator through a resonant circuit, and an ovcrspeed safety device mbodying a second resonant circuit is adapted to cut out said first motor circuit past the resonant frequency of said first circuit.

The foregoing and other objects and advantages will ap ear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawing wherein one embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purposes of illustration only and is not to be construed as defining the limits of the invention.

The single figure of the drawing is a diagrammatic view illustrating a control system embodying one form of the invention.

Referring now to the drawing, a two phase actuator motor generally designated by the numeral It has a fixed phase winding H and a variable phase winding l2. The rotor shaft 13 of the motor it controls an air servo M which in turn operates a throttle it, which governs. the how of driving fluid to a prime mover H5. The shaft l3 of the torque motor is turns against the force of a spring ll. There. is further provided an alternator l8 havin a permanent magnet Ill and three phase. stator windings 2t, 22, and 23, having output. conductors 24, and respectively and a center output conductor grounded at 29. The rotor 39 of the alternator it is on a common shaft M with the prime mover l5, and is. driven thereby.

The fixed phase winding 1! of the motor it is connected by means of conductors and 3 3 to the phase winding 2.3 of the alternator ill, and the variable phase winding 52 of the motor is also connected to the. winding 23 of alternator 18 through a series resonant circuit consisting of a conductor 36, the relay arm 38 of a proportional relay 30, the function of which is hereinafter explained, a conductor 12, 2. capacitance M, and an inductance 45, and a conductor joining the conductor 3d at post 552. It is to be noted that said circuit from the variable phase winding l2 through conductor 35, relay arm 38;, conductor 32, capacitance 44, inductance conductor 48, and conductor 3-; to the phase winding 23 of the alternator I8 is operative only when the relay arm 38 of the relay it connects terminals 54 and for when the relay arm 3.3 is in its opposite position, thereby connecting the, terminals 5 5 and ill, the variable phase windmg I2. oi the motor ill will be connected to phase winding 2i] of the alternator 18 by means of the conductor 33, the relay arm 38, and a conductor 53, thorehy cutting out the capacitance i and the inductance 46.

Another series resonant cricuit including the inductance 6t and the. capacitance 62 is connected across center output conductor and phase winding 22 of the alternator It by means of conductors (i l and 36. Rectifiers S8 and "if! are connected across the inductance 5i and the capacitance 32, respectively, and the coils 2'2 and M from rectifiers B8 and it), respectively, are wound about a permanent magnet E5 of the proportional relay 4%.

The relay 40 is of a type well known in the art and operates on the direct current output voltage from the rectifiers 6B and 7t impressed upon the coils 12 and 1'5, respectively. It is well known that the action of a variable frequency voltage on a series resonant circuit is such that at frequencies below the resonance point, the voltage drop across the capacitance is greater than the voltage drop across the inductance, and at frequencies above resonance the voltage drop across the inductance is greater. Use of this phenomenon is profitably made in the present invention, since by connecting the coils l2 and M as shown so as to have currents proportional to the voltage drop across the inductance and capacitance, respectively, the operation of the relay arm 38 will be governed by the differential current in the coils 12 and 14, thereby connecting terminal 54 to terminal 6 when the voltage drop across the capacitance is greater, and overcoming the tension in spring 18 to connect terminal 54 to terminal 5'! when the voltage drop across the inductance is greater.

As the frequency of the alternator [B which is driven by the prime mover It, increases due to an increase in the speed of the prime mover, there will be a proportional increase in the volt age across the variable phase winding [2 as the resonant frequency of the series resonant circuit comprising conductor 36, relay arm 38, conductor 42, capacitance 4t and inductance it and conductors 48 and 34 is approached, resulting in a proportional increase in output torque of the shaft 13 of the motor 19. The increased torque will overcome the tension of the spring ii and actuate the servo M to operate the throttle l5 in a speed decreasing direction. The tension in the spring I? is arranged so that at alternator voltage frequencies below and approaching the resonant frequency of the said circuit including capacitance 44 and inductance 36, the angular position of the rotor shaft I3 is proportional to the frequency of the voltage of the alternator R8 or to the speed of its driving prime mover it.

It will now be seen that since the rotor shaft 13 of the motor Ill controls the servo M to actuate the throttle IS, the speed of the prime mover it, and, therefore, of the alternator l8 may be controlled by the motor ill, so that with an increase in prime mover speed in excess of a prede termined value aifecting switch 38, power to the prime mover is decreased by closing the throttle l5, and with a decrease in prime mover speed below a predetermined value, power available to the prime mover I6 is increased by opening the throttle l5.

The manner in which overspeeding of the prime mover i6 is prevented is as follows:

The capacitance 44 and the inductance as are connected in series between the motor H] and the alternator l8 by means of conductor 3'5, relay arm 33 and conductors 42, Q8, and 34. As speed in the prime mover l6 increases towards a critical value or resonant frequency, the alternator l8 driven thereby will supply a higher frequency voltage to the second resonant series circuit comprising the conductor 66, inductance 6d, capacitance 62 and conductor 64!. The resonance point of the second resonant series circuit is tuned to the same frequency as the first resonant series circuit including capacitance M, inductance 4'5, and the variable phase 12. As the frequency of the voltage across said second resonant circuit goes above the resonance point of the circuit the voltage drop across the inductance E0 will be greater than across the capacitance '52 due to the aforementioned characteristics of series resonant circuits. The coil 1d, therefore, will receive a greater rectified voltage than the coil 12 and overcome the magnetic force of coil 12 and the tension of spring 78 to pull the relay arm 38 into contact with terminal 51 thereby cutting out the capacitance 44 and the inductance 46, and connecting the motor IE directly to the alternator [8 by means of conductor 36, relay arm 38 and '4 conductor 58. A voltage will, therefore, be impressed upon the two phase control motor ll] of proper phase so as to increase the motor torque to cause the servo l4 to close the throttle IE to its maximum closed position thereby cutting off the supply of driving fluid to the prime mover Hi to decrease the speed of the prime mover.

When the prime mover l6 slows down sufiiciently so that the frequency output voltage of the alternator I8 is below the resonance point of the circuit, the coil 12 conversely will overcome the coil 10 so that the relay 4!] will again be in position to connect terminal 54 to terminal 55, and the control motor [0 will again be connected to the alternator l8 through the first resonant circuit including inductance 46 and capacitance id to thereby provide a proportional control.

It will thus be apparent that there are provided means for regulating the speed of a prime mover by controlling a throttle by means of an electric motor responsive to the output of an alternator driven by said prime mover, and means for preventing overspeeding of said alternator by an improved resonant circuit control.

Although only one embodiment and one application of the invention has been illustrated and described, other changes and modifications in the form and relative arrangement of parts, which will be apparent to those skilled in the art, may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. In a speed governing device for alternator driven by a prime mover, the combination comprising a two phase torque motor, said motor being connected to said alternator, an inductance and a capacitance connected in series between said motor and said alternator, a proportional relay m series with said inductance and capacitance, a second inductance and capacitance connected in series to said alternator, rectifier means across said second capacitance and inductance, differential coils for actuating said relay, the output of said rectifier means being impressed on the differential coils of said relay to cut out said first inductance and capacitance and connect said torque motor directly to said alternator upon an increase in speed of said alternator and prime mover above a predetermined value.

2. In a speed governing device for an alternator, the combination comprising a torque motor, a circuit including an inductance and a capacitance in series connecting said motor to said alternator, a proportional relay in series with said inductance and capacitance, differential coils'for, actuating said relay, a second inductance and capacitance in series connected directly to said alternator, a rectifier connected across said second inductance to energize one of said coils and a rectifier connected across said second capacitance to energize another of said coils, said relay responsive to the output of said rectifiers to cut out said first inductance and capacitance and connect said motor directly to said alternator upon overspeeding of said alternator.

3. For use as a speed governing device for an alternator having a variable frequency alternating current output; the combination comprising a torque motor, a circuit having a predetermined resonant frequency and including an inductance and a capacitance connected in series for connecting said torque motor to the output of said alternator, a proportional relay having a switch element for normally connecting the output of said alternator to said torque motor through said inductance andcapacitance, a second inductance rectifier means connected across said second inductance and capacitance to impress a voltage on said relay at alternator output frequencies in excess of said predetermined resonant frequency to affect said switch element so as to cut out said first inductance and capacitance and connect said torque motor directly to said alternator to increase the torque of said motor.

4. For use as a speed governing device for an alternator having a variable frequency alternating current output; the combination comprising a torque motor, an inductance and a capacitance in a series resonant circuit for connecting said torque motor to the output of said alternator so as to proportionately increase the torque of said motor with increase in the output frequency of said alternator from a minimum to a resonant frequency, relay means for controlling said resonant circuit, differential electromagnetic means for operating the relay means, a second capacitance and inductance in a series resonant circuit for connection in the output of said alternator, rectifier means connecting said second capacitance and inductance across the differential electromagnetic means so as to operate said relay means in response to the output of said alternator to effect a maximum motor torque upon the output frequency of the alternator exceeding a predetermined value.

5. For use as a speed governing device for an alternator having a variable frequency alternating current output; the combination comprising a torque motor, a first resonant circuit for connecting said torque motor to the output of said alternator to proportionately increase the torque of the motor with alternator speed from a minimum to a resonant frequency, relay means for controlling said first resonant circuit, differential electromagnetic means for operating the relay means, and a second resonant circuit means connecting said electromagnetic means to the output of said alternator to energize said differential electromagnetic means so as to cause the relay means to discontinue the first resonant circuit upon the output frequency of the alternator exceeding a predetermined value.

ROBERT L. STALLARD.

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